The invention relates in general to the design of combustion engines, particularly compression-ignition internal combustion engines.
Emissions standards imposed on motor vehicle manufacturers are becoming increasingly severe, each change in a standard resulting in significant technical developments and in the use of additional and/or more complicated emissions-control devices which prove to be expensive.
Future standards are encouraging manufacturers especially to reduce the level of exhaust emissions of nitrogen oxides and particulates, notably in order not to clog the particulate filters too quickly, but the manufacturers are at the same time wishing to increase, or at least to maintain, the engine performance levels and drivability.
Solutions generally adopted to increase emissions control of engines for example consist in resorting to advanced post-treatment devices such as particulate filters or in modifying the exhaust gas recirculation specifications, the English acronym EGR being widely recognized in this field, although this has an adverse impact on engine efficiency.